A mechanism study on the tamoxifen-mediated cellular internalization of liposomes

他莫昔芬介导脂质体细胞内化的机制研究（英文）

It was reported previously that tamoxifen （TAM） could increase the intracellular accumulation of drug-loaded liposomes, but the exact mechanism is unknown although it was supposed that TAM might enhance the cell uptake by inhibiting the drug efflux caused by P-glycoprotein （P-gp）. To identify the mechanism of increased cellular uptake of liposomes induced by tamoxifen, PEGgylated liposomes （SSL） ofP-gp-substrate doxorubicin （DOX） or non-P-gp-substrate coumarin （Cou） were prepared with or without TAM. The cell uptake of these liposome systems was investigated in cell lines with different P-gp-expressing levels and the interaction of TAM with lipid membrane was also studied. As the results, the co-encapsulation of TAM with DOX-SSL increased the intracellular uptake in all three tumor cell lines. In P-gp-highly-expressing MCF-7/Adr cells, the effect of TAM was the strongest and in negative control Hela cells, the impact weakened but still significant. The improvement was also observed in the cellular uptake of Cou-SSL. Surface plasmon resonance （SPR） studies demonstrated that TAM-SSL exhibited a much stronger atYmity with model biomembrane compared with empty SSL, and ft^her test with isothermal titration calorimetry （ITC） showed that free TAM had an obvious interaction with lipid membrane. In conclusion, TAM could increase the affinity of liposomes with biomembrane and enhance the intracellular accumulation of liposomes via both TAM-mediated P-gp inhibition and the increased interaction between hydrophobic TAM molecules and lipid membrane.

文献报道他莫昔芬能够增强载药脂质体的细胞摄取,其具体机制仍有待研究,有研究者推测此现象是由他莫昔芬抑制P-糖蛋白对药物的外排作用而造成的。本研究为进一步阐明该作用的机理,制备了PEG修饰、共包载他莫昔芬的P-糖蛋白底物阿霉素脂质体及非底物香豆素-6脂质体,研究了不同P-糖蛋白表达水平的细胞对载药脂质体的摄取情况,及包载他莫昔芬后脂质体与脂膜的相互作用。结果表明,共包载他莫昔芬能显著提高所选三种细胞对阿霉素脂质体的摄取,且摄取增加水平与P-糖蛋白表达水平相关。同时,共包载他莫昔芬能显著增加非P-糖蛋白底物香豆素-6脂质体的摄取,对阿霉素脂质体在P-糖蛋白表达阴性的Hela细胞中的摄取也有显著促进作用。表面等离子共振技术证明他莫昔芬脂质体与模型生物膜的亲和力强于不载药的空白脂质体,等温滴定量热技术证明游离他莫昔芬与模型生物膜有明显亲和作用。综上,他莫昔芬能够增强脂质体和生物膜的亲和力,通过抑制P-糖蛋白对药物的外排、提高脂质体和细胞膜的结合两方面的共同作用提高细胞对脂质体的摄取。